Learn and Experiment
Measure your room’s clean-air performance
Use a PM2.5 decay test to estimate how quickly your space clears aerosol-sized particles — then see what it takes to reach a 12 ACH target.
Why “clean air” matters for viruses
Respiratory viruses can spread through the air in particles and aerosols generated by breathing, talking, coughing, and singing. Indoors, these aerosols can accumulate and remain suspended. Increasing clean air reduces airborne concentration over time.
It measures how quickly your room removes aerosol-sized particles under your conditions. It does not detect viruses directly. The result includes combined removal from filtration, outdoor-air exchange, and natural deposition to surfaces.
Where MERV 13 fits
MERV ratings describe filter performance across particle size ranges. MERV 13 is widely recommended as a practical minimum upgrade where systems can handle it, because it captures a meaningful fraction of fine particles in the same general size range as many respiratory aerosols.
Enter your test data
Start with a single run. If you can, do a second run with your air cleaner operating — that lets you measure the improvement directly.
How to collect readings (fast)
- Place your PM monitor at breathing height and away from vents.
- Record baseline PM2.5 (after it stabilises).
- Create a short, controlled particle spike and mix the room briefly with a plain fan.
- When the peak looks steady, start timing at Minute 0 and let the value fall.
- Add 2–4 readings while it drops (e.g., at 5, 10, 15, 20 minutes). More points = a better fit.
- Saltwater nebuliser (recommended): Use plain saline, or make it by dissolving a small amount of salt in clean water. Run the nebuliser briefly to raise PM2.5, then stop. Many PM sensors register these fine droplets reliably.
- Cooking that produces visible aerosol: Briefly sear something on the stovetop or toast a tortilla until you see a light haze. Stop the source completely before timing the decay. Avoid running a range hood during the decay unless it reflects your normal conditions.
- Incense: Light an incense stick for 30–60 seconds, then extinguish it and remove it from the room. Use mixed room air for readings — not the concentrated plume near the source.
- Candle (light → extinguish): Light a candle and blow it out to create a short puff of smoke. Repeat only until you reach a clear peak, then stop. Mix the room before starting the timer.
Run A — Your current conditions
Interpretation: higher effective ACH means faster removal of aerosol-sized particles from room air after the source stops.
What to do next to reach 12 ACH
If your measured ACH is below 12, you can increase clean air by adding capacity (more airflow through filters), improving placement, and improving mixing. The planner below turns your result into a simple “how much more do I need?” estimate.
- Add clean-air capacity (additional device / higher setting).
- Improve placement (clear intake/exhaust, avoid tight corners).
- Improve mixing (a small mixing fan often helps in closed rooms).
| Fan | Effective CFM | Fans for ~6 ACH | Fans for ~12 ACH |
|---|
Heads up: if your box has 4 / 6 / 7 fan slots, you’ll fill it with that many individual fans.
Disclaimer: Educational estimates only. Real results vary with airflow, filter loading, leakage/bypass, and room mixing.